Technical Abstract:
Channelized headwater streams are common throughout agricultural watersheds in the Midwestern United States. Management of these streams focuses on drainage without consideration of the other ecosystem services they are capable of providing. Restoration of channelized agricultural headwater streams is hindered by a lack of basic ecological information. Understanding fish-habitat relationships within channelized agricultural headwater streams will assist with designing restoration projects for these degraded streams. We have been conducting research involving fish community assessments, biomarker evaluations, and streamside bioassays from seven channelized agricultural headwater streams in central Ohio and three channelized agricultural headwater streams in northeastern Indiana since 2006. Our objective for this presentation is to synthesize seven years of research results to highlight how information on fish-habitat relationships can assist with designing restoration projects. Our fish community assessments have documented that community structure is more strongly correlated with instream habitat than either riparian habitat or water chemistry. These fish-habitat relationships occur across watersheds and within individual watersheds. However, examination of fish-habitat relationships within individual watersheds revealed some within-watershed differences. Six of 21 fish community response variables were more strongly correlated with water chemistry in northeastern Indiana and only one of 20 response variables was more strongly correlated with water chemistry in central Ohio. Results from streamside bioassays suggest that long-term exposure to nutrients and herbicides may have caused negative impacts on growth in fathead minnows (Pimephales promelas). However, exposure to agricultural contaminants did not affect survival, hepatosomatic index , or gonadosomatic index in fathead minnows. Overall, our results suggest that restoration projects within channelized agricultural headwater streams in the Midwestern United States need to address physical habitat degradation to induce changes in fish community structure and to address chemical habitat degradation to avoid sublethal responses in fish populations.